Incrementing VERSION to 71.0.3578.12

TBR=benmason@chromium.org

Change-Id: I432f0ee0d7fd69e8af6f66908c1571abed4ec5b7
Reviewed-on: https://chromium-review.googlesource.com/c/1286746
Reviewed-by: chrome-release-bot@chromium.org <chrome-release-bot@chromium.org>
Cr-Commit-Position: refs/branch-heads/3578@{#93}
Cr-Branched-From: 4226ddf-refs/heads/master@{#599034}

chrome/VERSION

@@ -1,4 +1,4 @@
 MAJOR=71
 MINOR=0
 BUILD=3578
-PATCH=11
+PATCH=12